Media Center on Microcontroller
In this project, a Media Center was implemented on MCB 1700 board with LPC1768 microcontroller onboard, an ARM Cortex-M3 processor clocked at 150MHz, 512Kb on-chip flash, joystick, and an LCD for graphical interface. The development was done using MDK (Microcontroller Development Kit) The graphical interphace was implemented on the LCD, with its functionality including:
- A Photo Gallery
- An mp3 player
- Games
Media Center layout
To keep track of the different functionalities selected by the user,
a global variable page was created, page=0 being the home menu.
The variable page will get updated based on the user’s choices. Along with
the page number, a line, which is also a global variable that was created to track
the user's selection from the options provided (Audio stream, Photos, Game) and display the selected option by calling its function.
The crusor ">" was to help the user navigate the media center, and is controlled using the joystick on the board.
Audio Streaming
After the user selects the “Audio Streaming” option from the media center’s homepage, a custome-made function will be called to start streaming audio via USB from the PC to the dev board. The USB was used to connect to the PC, and disconnect when signaled to exit from the player, it worked by disabling the NVIC (Nested Vectored Interrupt Controller) that was responsible for starting the stream. The potentiometer on the board was used as adjust the volume of the on-board speaker. Counter clockwise rotation of the pot increases the volume, whereas clockwise rotation to the pot decreases the volume.
Photo Gallery
The pictures that ere to be displayed on the LCD has to be converted to bitmaps, which were then converted to a C file that is then read into the program as an array of unsigned chars- unsigned char can hold a value in the range of 0 to 255, which is enough to represent 8-bit images. The LCD had a resolution of 640x420px, which meant that the images had to be resized before turned into a bitmap in order to fit the LCD perfectly.
Game
This part of the Media Menter was the biggest in term of memory usage. The game that was implemented was a modified version of Highway Madness. The premise behind the game was that a user controls a car (with the joystick) and try to avoid other cars while also trying to get as many gold coins as possible, then those gold coins would be used to unlock more images from the Photo Gallery as a reward system.
First to set the environment (Highway and cars), stock photos of a three–line highways, and cars were edited so they can fit onto the LCD.
The cars were superimposed on the background (the three-lane highway). The user is resnponsible for controlling the purple
car at the bottom while the CPU handles all other cars. The user can move
the car up, down, left, and right by using the joystick. Each car had it own function.
For collision detection, 3 variables: front_bumper,rear_bumper, and lane were created to represent the cars and move them around the LCD.
If the user’s car front_bumper value is in between rear_bumper, and front_bumper of the CPU-controlled car
and both cars are at the same lane, then a collision has occurred,
and thus the game is over. As for the gold coin, it generates randomly on the screen with the
help of the rand()
function in C. The user’s score will be updated once the position of the gold coin
is between the front_bumper, and rear_bumper of the user’s car, and have the same lane value.
User's Car
This function is responsible for polling the joystick's value and responds accordingly.
If the user pressed right on the joystick, the function will delete the user’s car
in it current position and prints it on the right lane while also updating the values
for the front_bumper, and rear_bumper.
CPU-controlled cars
Each time a CPU-controlled car function is called, the car is moved by 20px downwards towards the user’s car.
Gold coin
When collision between the user’s car and the gold coin is detected, a variable score will be incremented by one.
After that the coin will be generated randomly on the LCD
